Lawyers working for former Trump Campaign manager and convicted felon, Paul Manafort filed a document yesterday that contains the clearest public evidence to date of coordination between the Trump’s 2016 presidential campaign and the Russians.

The lawyers did not intend to release this evidence. The admissions are located deep in a court filing prepared in response to Special Counsel ripping up the plea agreement. The admissions contain facts that the OSC alleges Manafort continued to make false statements after signing the plea deal. So what happened?

It is now well-established that Paul Manafort is not good with technology. But it’s Manafort’s lawyers who made a mistake here. They submitted a PDF that had black boxes drawn over the text to be redacted but without deleting the actual text underneath it.

We cannot know why this happened. We do not know who prepared the PDF and what method was used to finally render it. But there are some things we do know.

What is a PDF?

PDF is the file extension and abbreviation for Portable Document Format. This format was developed by the Adobe Software corporation in the early 1990s. It is designed to be a software agnostic format to view documents as they were initially designed and intended by their authors. PDFs have played a critical role in the move from physical paper to digital formats. It has been and remains the standard format for electronically sending a document.

How can you redact PDFs?

When lawyers need to redact parts of documents, the best, most foolproof way to do so is to delete the text in the underlying document and replace it by typing in [REDACTED].

When this isn’t feasible, it is possible to export the PDF into an image file format (aka going from vector to raster), redact the image, and produce the flattened image. The images can be produced as is or combined into a new PDF file.

Alternatively, Acrobat Pro does offer tools to redact PDFs properly — but as we have seen these are hardly failsafe. It’s a bit of a learning curve. Not insurmountable, but a curve nonetheless.

Why did Manafort’s lawyers fail to redact properly?

It’s impossible to know for sure. Did they want the information out? Perhaps, seems like an awfully blunt method to leak information. Examining the underlying document, it appears the law firm used Adobe Acrobat Pro’s markup tools to draw a black box over the text. The proper workflow is to use Acrobat’s purpose-built Redaction tools Adobe provides in the Protection menu. It’s an educated guess but given the ubiquity of Acrobat Pro usage in law firms, it makes sense.

How can I keep from doing this?

Lawyers often ask us how we can help prevent this from happening during eDiscovery. And, it’s fair to debate what Adobe could do to prevent users from making this mistake. The software does provide alternative tools that meet these requirements. Additionally, it does have warning dialog boxes when users access features that could be mistaken for fully redacting. But ultimately, it is a real problem when users *think* they used a feature in software when what happened is opposite of the user intention. If the program saves a file when the user hits the delete button, that’s an issue.

Using litigation support software (and not using Acrobat Pro for redactions) is a sensible approach. At a minimum, if a law firm is going to insist on using Acrobat Pro—generally from a misguided effort to save money—a substantial investment must be made to train users to avoid this critical error.